Crossover

A crossover is a story in which the Doctor Who universe is combined with elements from another fictional universe. Although fictional characters have appeared as such within the Doctor Who universe (for example, in the Land of Fiction), characters from other works have, from time to time, become involved.

The continuity of these specials has been questioned by some fans, especially EastEnders, which was revealed in Army of Ghosts to be fiction in the Doctor Who universe, just as characters like the Doctor and the Daleks are fictional in the continuity of EastEnders. It is truly up to each fan to decide which stories do and do not count.

In No Future, mention is made of a Soviet military group called the Vodyanoi. This is a reference to the David Wiltshire novel Child of Vodyanoi, which was adapted into the TV series The Nightmare Man.

In Millennial Rites, there are brief appearances of a man in a blue cloak levitating in an old brownstone in New York, and a blond-haired man in a dirty beige trenchcoat having a Guinness in a Dublin bar. These are meant to be the comic book magicians Doctor Strange and John Constantine.

In Happy Endings, Bernice meets a teenage girl dressed in black with dark hair who seems familiar to her. The girl says that her job is to turn off the lights once everybody's gone. The girl is intended to be Death from Neil Gaiman's The Sandman.

In The Face of the Enemy, mention is made of an English village named Little Storping. A village with the same name appears in "Murdersville", an episode of The Avengers.

In The Fall of Yquatine, Fitz is said to have worked at the Mother Black Cap in Camden Town in the 1960s. This is a reference to the film Withnail and I, which is set in the same time period and features a pub of the same name in the same location.

In Verdigris, Jo Grant reminisces about her friend Tara, with whom she'd gone to spy school and who was also assistant to an eccentric freelance gentleman adventurer in secret service to the government. This is clearly meant to be Tara King of The Avengers.

In The Gallifrey Chronicles, a copy of the first Harry Potter novel in the Doctor's TARDIS has the first page crossed out and the words "No, no, no, no, it didn't happen like this at all" written on it in red ink, implying that the Doctor knows how it did happen.

In Omegamorphosis, mention is made of Gregor Samsa, who turned into an insect, and whose story was written by his friend. This is a reference to The Metamorphosis.

In Forever Autumn the Doctor claims to have met Jar Jar Binks' clan, and that George Lucas mistook a telepathic message for his own ideas, implying that the Star Wars stories were based on real events.